This project is the creation of the Collaborative National Network Examining Comparative effectiveness Trials or CoNNECT by combining two existing national networks devoted to studying primary care. The Collaborative Care Research Network (CCRN) is a national network that seeks to advance effectiveness research on collaborative care, defined as the integration of mental health, substance abuse, and behavioral health services into primary care. The CCRN is affiliated with an electronic practice-based research network, the Distributed Ambulatory Research and Therapeutics Network (DARTNet), which was created with funding from the Agency for Healthcare Research and Quality's Developing Evidence to Inform Decisions about Effectiveness Network. DARTNet enables comparative effectiveness research by extracting and standardizing clinical data from multiple electronic health record systems across numerous institutions. This proposal harnesses the power of DARTNet and formalizes the relationship between DARTNet and the CCRN to enhance the CCRN's capabilities to conduct comparative effectiveness research on mental health, behavioral health, and substance use in primary care. The resulting structure-the intersection between DARTNet and the CCRN-creates the Collaborative National Network Examining Comparative effectiveness Trials (CoNNECT). There are three aims associated with this project: Aim 1: Establish and test CoNNECT;Aim 2: Demonstrate the effectiveness of the infrastructure and its capacity by conducting a research project to evaluate the care of people with expensive chronic diseases complicated by comorbid mental health, behavioral health, and substance use problems;Aim 3: Evaluate CoNNECT to determine it strengths, weaknesses and potential for extensive comparative effectiveness research, with patients from underrepresented groups, with both depression or other mental conditions AND other priority chronic medical conditions. PUBLIC HEALTH RELEVANCE: CoNNECT will answer important questions about patients with depression, substance abuse and other chronic medical illnesses, who receive care in diverse geographic regions and types of practices. Cutting-edge electronic health record technology will be used to generate data on large patient populations for comparative effectiveness studies.